Nitrogen defect type carbon nitride quantum dot / bismuth defect type bismuth oxybromide heterojunction as well as preparation method and application thereof

Abstract

The invention relates to the technical field of composite photocatalysts, in particular to a nitrogen defect type carbon nitride quantum dot / bismuth defect type bismuth oxybromide heterojunction and a preparation method and application thereof.The preparation method includes the steps that urea and sodium citrate are heated, washed, centrifuged, frozen and dried to obtain nitrogen defect type carbon nitride quantum dots; dissolving nitrogen defect type carbon nitride quantum dots in ethylene glycol to obtain a first solution; adding bismuth nitrate pentahydrate into the first solution to obtain a second solution; dissolving a template agent in a mixed solution of ammonia water and deionized water to obtain a third solution; adding the third solution into the second solution, and carrying out hydrothermal reaction to obtain a second reaction product; and washing and centrifuging the second reaction product, and freeze-drying to obtain the nitrogen defect type carbon nitride quantum dot / bismuth defect type bismuth oxybromide heterojunction. The synthesized nitrogen defect type carbon nitride quantum dot / bismuth defect type bismuth oxybromide heterojunction has a remarkable effect in the aspect of photocatalytic reduction of CO2 into CO, and has the advantages of high light utilization rate and high electron hole pair separation rate.

Description

Technical Field

[0001] The invention relates to the technical field of composite photocatalysts, and is a nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction, and a preparation method and application thereof. Background Art

[0002] With the continuous growth of the world's population and the significant improvement of human living standards, energy consumption has increased rapidly in recent decades, leading to excessive greenhouse gas emissions, mainly carbon dioxide. Inspired by photosynthesis in nature, photocatalytic reduction of carbon dioxide is considered to be one of the ideal solutions to this problem.

[0003] Directly capturing carbon dioxide from ambient air and converting it into value-added fuels using photocatalysis is a potentially valuable technology. However, there are still many challenges to overcome in order to achieve direct photocatalytic reduction of carbon dioxide from air. For example, low concentrations of carbon dioxide are difficult to be effectively adsorbed and activated on the surface of most photocatalysts, and some catalysts require anaerobic atmospheres to prevent undesirable oxidation reactions from occurring.

[0004] Bismuth oxyhalide, as a newly developed semiconductor photocatalyst, has an adjustable sunlight absorption range and is often used for photocatalytic carbon dioxide reduction. However, single bismuth oxyhalide photocatalysts have a high recombination rate of photogenerated carriers. Although strategies such as heteroatom doping and morphology control have been adopted to improve the separation efficiency of photogenerated charges, it is still a challenge to simultaneously obtain high visible light utilization, effective charge separation, and strong redox ability.

[0005] The heterojunction of CNQDs (carbon nitride quantum dots) and bismuth-based compounds has been reported in the literature and applied to the field of photocatalysis. For example, Zhang et al. (J Colloid Interf Sci 539 (2019) 654–664) constructed a CNQDs / Bi2WO6Z heterojunction. Under visible light irradiation, the removal rates of TC (tetracycline) and RhB (rhodamine B) can reach 87% and 92.51% within 60 minutes, and it can still play a certain role in the degradation of TC (tetracycline) under near-infrared (NIR) light. In addition, Tao Feifei's research group (MaterSci Semicond Process172 (2024) 108058) successfully synthesized CNQDs / BiVO4 composite materials. The upconversion luminescence of CNQDs can induce BiVO4 to produce more photogenerated electrons to participate in the photodegradation reaction of MO.

[0006] At present, in the field of photocatalytic reduction of low-concentration carbon dioxide technology, the heterojunction of CNQDs (carbon nitride quantum dots) and bismuth-based compounds generally has the problems of low light utilization efficiency and low electron-hole pair separation rate, and it is urgent to develop new photocatalysts to solve these problems. Summary of the invention

[0007] The present invention provides a nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction and a preparation method and application thereof, which overcome the deficiencies of the above-mentioned prior art and can effectively solve the problems of low light utilization rate and low electron-hole pair separation rate in the existing photocatalytic reduction of low-concentration carbon dioxide.

[0008] One of the technical solutions of the present invention is achieved by the following measures: a nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction is prepared according to the following method: the first step is to mix and grind a required amount of urea and sodium citrate, and then heat to obtain a first reaction product; the second step is to wash the first reaction product with anhydrous ethanol and centrifuge it, then dissolve it in deionized water for dialysis, freeze it and then dry it to obtain nitrogen-deficient carbon nitride quantum dots; the third step is to dissolve the required amount of nitrogen-deficient carbon nitride quantum dots in ethylene glycol, and ultrasonically treat it to obtain a first solution; the fourth step is to The first step is to add the required amount of bismuth nitrate pentahydrate to the first solution to obtain a second solution; the fifth step is to dissolve the required amount of template agent hexadecyltrimethylammonium bromide in a mixed solution of ammonia water and deionized water to obtain a third solution; the sixth step is to add the third solution to the second solution to carry out a hydrothermal reaction to obtain a second reaction product; the seventh step is to cool the second reaction product to room temperature, wash it with deionized water and anhydrous ethanol, and centrifuge it to obtain a solid precipitate; the eighth step is to freeze and dry the solid precipitate to obtain a nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction.

[0009] The following is a further optimization and / or improvement of one of the above-mentioned technical solutions: In the first step, 2.94 g of sodium citrate was added to every 3.6 g of urea and mixed evenly. The grinding time was 10 min, and then heated to 180° C. and kept warm for 1 h.

[0010] In the above second step, the washing times with anhydrous ethanol are 3 times.

[0011] In the third step, 70 mg of nitrogen-deficient carbon nitride quantum dots were dissolved in 20 mL of ethylene glycol, and the ultrasonic treatment time was 30 min.

[0012] In the fourth step, 0.97 g of bismuth nitrate pentahydrate was added to every 70 mg of nitrogen-deficient carbon nitride quantum dots.

[0013] In the fifth step, 0.97 g of bismuth nitrate pentahydrate was added to every 0.728 g of the template agent hexadecyltrimethylammonium bromide.

[0014] In the sixth step, the hydrothermal reaction temperature is heated to 120°C and kept for 3 hours.

[0015] In the seventh step, the washing times with deionized water and anhydrous ethanol are both 3 times.

[0016] The second technical solution of the present invention is achieved by the following measures: a method for preparing a nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction, which is carried out according to the following method: the first step is to mix and grind the required amount of urea and sodium citrate, and then heat to obtain a first reaction product; the second step is to wash the first reaction product with anhydrous ethanol and centrifuge it, then dissolve it in deionized water for dialysis, freeze it and then dry it to obtain nitrogen-deficient carbon nitride quantum dots; the third step is to dissolve the required amount of nitrogen-deficient carbon nitride quantum dots in ethylene glycol, and ultrasonically treat it to obtain a first solution; the In the fourth step, a required amount of bismuth nitrate pentahydrate is added to the first solution to obtain a second solution; in the fifth step, a required amount of template agent hexadecyltrimethylammonium bromide is dissolved in a mixed solution of ammonia water and deionized water to obtain a third solution; in the sixth step, the third solution is added to the second solution to carry out a hydrothermal reaction to obtain a second reaction product; in the seventh step, the second reaction product is cooled to room temperature, washed with deionized water and anhydrous ethanol, and centrifuged to obtain a solid precipitate; in the eighth step, the solid precipitate is frozen and dried to obtain a nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction.

[0017] The third technical solution of the present invention is the application of a nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction in the photocatalytic reduction of carbon dioxide to carbon monoxide products.

[0018] The present invention adopts a hydrothermal method to synthesize a nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction. Under the irradiation of simulated sunlight, the nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction has a significant effect in photocatalytic reduction of CO2 to CO, and has the advantages of high light utilization rate and high electron-hole pair separation rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Attached Figure 1 V Bi -Bi4O5Br2、V N -CNQDs, V N -CNQDs / V Bi -XRD and EPR patterns of Bi4O5Br2 heterojunction; Attached Figure 2 V Bi -Bi4O5Br2、V N -CNQDs / V Bi -TEM image of Bi4O5Br2 heterojunction; Attached Figure 3 V Bi -Bi4O5Br2、V N -CNQDs, V N-CNQDs / V Bi -Photonic absorption performance diagram of Bi4O5Br2 heterojunction; Attached Figure 4 V Bi -Bi4O5Br2 and V N -Band structure diagram of CNQDs; Attached Figure 5 V Bi -Bi4O5Br2、V N -CNQDs, V N -CNQDs / V Bi -Photocatalytic CO2 reduction performance diagram of Bi4O5Br2 heterojunction in air atmosphere. DETAILED DESCRIPTION

[0020] The present invention is not limited by the following embodiments, and the specific implementation method can be determined according to the technical scheme of the present invention and the actual situation. Unless otherwise specified, the various chemical reagents and chemicals mentioned in the present invention are all chemical reagents and chemicals known and used in the prior art; unless otherwise specified, the percentages in the present invention are all mass percentages; unless otherwise specified, the solutions in the present invention are all aqueous solutions with water as the solvent, for example, hydrochloric acid solution is a hydrochloric acid aqueous solution; the normal temperature and room temperature in the present invention generally refer to a temperature of 15°C to 25°C, and are generally defined as 25°C.

[0021] The present invention will be further described below in conjunction with embodiments: Example 1: The nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction is prepared according to the following method: the first step is to mix and grind the required amount of urea and sodium citrate, and then heat to obtain a first reaction product; the second step is to wash the first reaction product with anhydrous ethanol and centrifuge it, then dissolve it in deionized water for dialysis, freeze it and then dry it to obtain nitrogen-deficient carbon nitride quantum dots; the third step is to dissolve the required amount of nitrogen-deficient carbon nitride quantum dots in ethylene glycol, and ultrasonically treat it to obtain a first solution; the fourth step is to mix the required amount of pentahydrate Bismuth nitrate is added to the first solution to obtain a second solution; in the fifth step, a required amount of template agent hexadecyltrimethylammonium bromide is dissolved in a mixed solution of ammonia water and deionized water to obtain a third solution; in the sixth step, the third solution is added to the second solution to carry out a hydrothermal reaction to obtain a second reaction product; in the seventh step, the second reaction product is cooled to room temperature, washed with deionized water and anhydrous ethanol, and centrifuged to obtain a solid precipitate; in the eighth step, the solid precipitate is frozen and then dried to obtain a nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction.

[0022] The molecular formula of the nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction in the present invention is V N -CNQDs / V Bi-Bi4O5Br2 heterojunction.

[0023] Example 2: As an optimization of the above example, in the first step, 2.94 g of sodium citrate was added to every 3.6 g of urea and mixed evenly, the grinding time was 10 min, and then heated to 180° C. and kept warm for 1 h.

[0024] Example 3: As an optimization of the above example, in the second step, the number of washing times with anhydrous ethanol is 3 times.

[0025] Example 4: As an optimization of the above example, in the third step, 70 mg of nitrogen-deficient carbon nitride quantum dots were dissolved in 20 mL of ethylene glycol, and the ultrasonic treatment time was 30 min.

[0026] Example 5: As an optimization of the above example, in the fourth step, 0.97 g of bismuth nitrate pentahydrate is added to every 70 mg of nitrogen-deficient carbon nitride quantum dots.

[0027] Example 6: As an optimization of the above example, in the fifth step, 0.97 g of bismuth nitrate pentahydrate is added to every 0.728 g of the template agent hexadecyltrimethylammonium bromide.

[0028] Example 7: As an optimization of the above example, in the sixth step, the hydrothermal reaction temperature is heated to 120°C and kept warm for 3 hours.

[0029] Example 8: As an optimization of the above example, in the seventh step, the washing times with deionized water and anhydrous ethanol are both 3 times.

[0030] Example 9: The preparation method of the nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction is carried out according to the following method: the first step is to mix and grind the required amount of urea and sodium citrate, and then heat to obtain a first reaction product; the second step is to wash the first reaction product with anhydrous ethanol and centrifuge it, then dissolve it in deionized water for dialysis, freeze it and then dry it to obtain nitrogen-deficient carbon nitride quantum dots; the third step is to dissolve the required amount of nitrogen-deficient carbon nitride quantum dots in ethylene glycol, and ultrasonically treat it to obtain a first solution; the fourth step is to add the required amount of pentahydrate The method comprises the following steps: adding bismuth nitrate to the first solution to obtain a second solution; in the fifth step, dissolving the required amount of template agent hexadecyltrimethylammonium bromide in a mixed solution of ammonia water and deionized water to obtain a third solution; in the sixth step, adding the third solution to the second solution to carry out a hydrothermal reaction to obtain a second reaction product; in the seventh step, cooling the second reaction product to room temperature, washing it with deionized water and anhydrous ethanol, and centrifuging it to obtain a solid precipitate; in the eighth step, freezing and drying the solid precipitate to obtain a nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction.

[0031] Example 10: Application of the nitrogen-deficient carbon nitride quantum dots / bismuth-deficient bismuth oxybromide heterojunction in the photocatalytic reduction of carbon dioxide to carbon monoxide products.

[0032] Example 11: The preparation method of the nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction is prepared according to the following method: the first step is to mix and grind 3.6g of urea and 2.94g of sodium citrate for 10 minutes, put it into a muffle furnace, heat it to 180°C, and keep it warm for 1 hour to obtain a first reaction product; the second step is to wash the first reaction product three times with anhydrous ethanol and centrifuge it, then dissolve it in deionized water for dialysis, freeze it and then dry it to obtain nitrogen-deficient carbon nitride quantum dots; the third step is to dissolve 70mg of nitrogen-deficient carbon nitride quantum dots in 20mL of ethylene glycol, and ultrasonically treat it for 30 minutes to obtain a first solution; the fourth step is to add 0.97g of bismuth nitrate pentahydrate to the first solution to obtain a second solution; in the fifth step, 0.728 g of the template agent hexadecyltrimethylammonium bromide is dissolved in a mixed solution of ammonia water and deionized water to obtain a third solution; in the sixth step, the third solution is added to the second solution, and then transferred to a reactor with a volume of 50 ml of a polytetrafluoroethylene stainless steel liner, and the reactor is placed in an oven and heated to 120° C. and kept warm for 3 hours to perform a hydrothermal reaction to obtain a second reaction product; in the seventh step, the second reaction product is cooled to room temperature and then transferred to a centrifuge tube, washed with deionized water and anhydrous ethanol for 3 times and centrifuged to obtain a solid precipitate; in the eighth step, the solid precipitate is frozen and dried to obtain a nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction.

[0033] According to Example 11 of the present invention, V N -CNQDs / V Bi -Bi4O5Br2 heterojunction, the following photocatalytic activity tests were carried out, as shown in the attached Figure 1 , 2 , 3, 4, 5 as shown: Depend on Figure 1 It can be seen that V N -CNQDs / V Bi -Bi4O5Br2 heterojunction has high crystallinity, V N -CNQDs / V Bi -The characteristic stretching vibration peaks belonging to Bi4O5Br2 and CNQDs can be clearly observed in the Bi4O5Br2 heterojunction, and CNQDs contain nitrogen vacancies, while Bi4O5Br2 contains bismuth vacancies; Depend on Figure 2 It can be seen that V Bi -Bi4O5Br2 has a disordered structure composed of nanosheets. N -CNQDs / V Bi-Bi4O5Br2 heterojunction, the morphology changes to a flower-like structure composed of nanosheets; Depend on Figure 3 It can be seen that with V Bi -Bi4O5Br2、V N Compared with CNQDs, V N -CNQDs / V Bi -Bi4O5Br2 heterojunction can absorb a wider range of the sunlight spectrum; Depend on Figure 4 It can be seen that the test V Bi -Bi4O5Br2 and V N -CNQDs flat band potential and further analyzed its band gap structure, V Bi -The conduction band potential (ECB) of Bi4O5Br2 is -0.77 eV vs. NHE, V N -CNQDs have a conduction band potential (ECB) of -1.28 eV vs. NHE, V Bi -Bi4O5Br2 has a valence band potential (EVB) of 1.33 eV vs. NHE, V N -The valence band potential (EVB) of CNQDs is 0.1 eV vs. NHE; Depend on Figure 5 It can be seen that under the conditions of simulated sunlight irradiation and pure air atmosphere, 50 mg of V N -CNQDs / V Bi -Bi4O5Br2 heterojunction and 50mg V Bi -Bi4O5Br2 for photocatalytic CO2 reaction. N -CNQDs / V Bi The yield of CO generated by photocatalytic CO2 reduction of -Bi4O5Br2 heterojunction is 16.89 μmol g -1 h -1 , is V Bi -Bi4O5Br2 photocatalytic CO2 reduction to produce CO yield 9 times.

[0034] In summary, under the conditions of simulated sunlight and pure air atmosphere, V N -CNQDs / V Bi -Bi4O5Br2 heterojunction has a significant effect in the photocatalytic reduction of CO2 to CO.

[0035] The above technical features respectively constitute various embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. A nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction, characterized in that The preparation method is as follows: the first step is to mix and grind the required amount of urea and sodium citrate, and then heat to obtain a first reaction product; the second step is to wash the first reaction product with anhydrous ethanol and centrifuge it, then dissolve it in deionized water for dialysis, freeze it and then dry it to obtain nitrogen-deficient carbon nitride quantum dots; the third step is to dissolve the required amount of nitrogen-deficient carbon nitride quantum dots in ethylene glycol, and ultrasonically treat it to obtain a first solution; the fourth step is to add the required amount of bismuth nitrate pentahydrate to the first solution to obtain a second solution; the fifth step is to dissolve the required amount of template agent hexadecyltrimethylammonium bromide in a mixed solution of ammonia water and deionized water to obtain a third solution; the sixth step is to add the third solution to the second solution, and perform a hydrothermal reaction to obtain a second reaction product; the seventh step is to cool the second reaction product to room temperature, wash it with deionized water and anhydrous ethanol, and centrifuge it to obtain a solid precipitate; In the eighth step, the solid precipitate is frozen and then dried to obtain a nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction.

2. The nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction according to claim 1, characterized in that In the first step, 2.94 g of sodium citrate was added to every 3.6 g of urea and mixed evenly. The grinding time was 10 min, and then heated to 180° C. and kept warm for 1 h.

3. The nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction according to claim 1 or 2, characterized in that In the second step, the absolute ethanol washing times were 3 times.

4. The nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction according to claim 1, 2 or 3, characterized in that In the third step, 70 mg of nitrogen-deficient carbon nitride quantum dots were dissolved in 20 mL of ethylene glycol and the ultrasonic treatment time was 30 min.

5. The nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction according to claim 1, 2, 3 or 4, characterized in that In the fourth step, 0.97 g of bismuth nitrate pentahydrate was added to every 70 mg of nitrogen-deficient carbon nitride quantum dots.

6. The nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction according to any one of claims 1 to 5, characterized in that In the fifth step, 0.97 g of bismuth nitrate pentahydrate was added per 0.728 g of the template agent hexadecyltrimethylammonium bromide.

7. The nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction according to any one of claims 1 to 6, characterized in that In the sixth step, the hydrothermal reaction temperature was heated to 120°C and kept for 3 h.

8. The nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction according to any one of claims 1 to 7, characterized in that In the seventh step, the deionized water and anhydrous ethanol washing times are both 3 times.

9. A method for preparing a nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction according to any one of claims 2 to 8, characterized in that The method is as follows: the first step is to mix and grind the required amount of urea and sodium citrate, and then heat to obtain a first reaction product; the second step is to wash the first reaction product with anhydrous ethanol and centrifuge it, then dissolve it in deionized water for dialysis, freeze it and then dry it to obtain nitrogen-deficient carbon nitride quantum dots; the third step is to dissolve the required amount of nitrogen-deficient carbon nitride quantum dots in ethylene glycol, and ultrasonically treat it to obtain a first solution; the fourth step is to add the required amount of bismuth nitrate pentahydrate to the first solution to obtain a second solution; the fifth step is to dissolve the required amount of template agent hexadecyltrimethylammonium bromide in a mixed solution of ammonia water and deionized water to obtain a third solution; the sixth step is to add the third solution to the second solution, and perform a hydrothermal reaction to obtain a second reaction product; the seventh step is to cool the second reaction product to room temperature, wash it with deionized water and anhydrous ethanol, and centrifuge it to obtain a solid precipitate; In the eighth step, the solid precipitate is frozen and then dried to obtain a nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction.

10. Use of the nitrogen-deficient carbon nitride quantum dot / bismuth-deficient bismuth oxybromide heterojunction according to any one of claims 1 to 8 in the photocatalytic reduction of carbon dioxide to carbon monoxide products.

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